Distance-Constraint k-Nearest Neighbor Searching in Mobile Sensor Networks.

Abstract

The -Nearest Neighbors (NN) query is an important spatial query in mobile sensor networks. In this work we extend kNN to include a distance constraint, calling it a -distant -nearest-neighbors (-NN) query, which finds the sensor nodes nearest to a query point that are also at or greater distance from each other. The query results indicate the objects nearest to the area of interest that are scattered from each other by at least distance l. The -NN query can be used in most NN applications for the case of well distributed query results. To process an -NN query, we must discover all sets of NN sensor nodes and then find all pairs of sensor nodes in each set that are separated by at least a distance . Given the limited battery and computing power of sensor nodes, this -NN query processing is problematically expensive in terms of energy consumption. In this paper, we propose a greedy approach for -NN query processing in mobile sensor networks. The key idea of the proposed approach is to divide the search space into subspaces whose all sides are . By selecting sensor nodes from the other subspaces near the query point, we guarantee accurate query results for -NN. In our experiments, we show that the proposed method exhibits superior performance compared with a post-processing based method using the NN query in terms of energy efficiency, query latency, and accuracy.